Cigarette Package Provided With Internal Envelops Made From Polymer Film

ABSTRACT

The invention relates to a single-layered or multilayered, biaxially-oriented film which contains 70 to 100% by weight of polymer consisting of at least one type of aliphatic polyhydroxycarboxylic acid, and which is used in the form of an inner liner of a cigarette package.

The invention concerns a cigarette packaging comprising at least oneouter packaging and an inner wrapping for cigarettes. The inventionfurthermore concerns an inner liner.

Cigarette packagings are conventionally constructed in such a way thatthe packaging contents, namely a collection of cigarettes, aresurrounded by an inner wrapping. In the prior art, this inner wrappingconsists of a cut sheet of aluminium foil, an aluminium-paper laminationor a piece of metallised paper. This inner wrapping is often imprintedor embossed. Earlier cut sheets are today conventionally replaced byinner wrappings made of paper. The inner wrapping is often imprinted ormetallised, if necessary in combination with embossment, on the outside.

When manufacturing the packaging, the cigarettes are wrapped in thisinner wrapping, the so-called inner liner, and the wrapped collection ofcigarettes are folded by the packaging machine with the outer packaging,for example a flip-top lid packaging or a paper label.

The inner liner can consist of printed paper, metallised paper or otherlamellar materials. These materials are pulled onto the packagingmachine off a roll and cut to the appropriate length. If necessary,selected perforations are made in order to produce a target cut-offpoint which makes possible a selected tearing open of the inner linerupon first opening of the packaging.

Paper and metal films are particularly advantageous because of thefolding properties and the tearing properties. In this type of use, thestrips of material must feature good folding properties (dead-fold)which ensure that the cigarettes being wrapped are wrapped up fin enoughto remain as a bundle up until the point at which the outer packaging isput in place. Furthermore, the tearing behaviour performs an importantrole, in that a controlled opening of the liner is ensured. Finally, thecuts must feature a good flatness, in order that the handling is nothindered by the strips of material furling up.

This set of properties is well fulfilled by paper and metallised papers.Film made of thermoplastic polymers have inherently poor foldingproperties and therefore are generally not suitable material for thisusage. Moreover, plastic films in the form of small cuts tend to curlup, i.e. these cuts roll up along or across the length of the film stripall by themselves.

As plastic films nevertheless often have advantages over paper both fromthe point of view of environmental aspects and in terms of cost, thesubstitution of paper in various uses is a request constantly put to thefilm manufacturer.

So underlying the invention was the task of making available a filmsuitable for use as the inner liner of cigarette packaging, and whichmet the demands of this usage.

This task is solved by the use of a single-layered or multilayered,biaxially-oriented film as the inner liner of a cigarette packaging,such that the film contains 70 to 100% by weight of a polymer made of atleast one aliphatic hydroxyl carboxylic acid.

The invention comes into use particular for flip packs and softpackaging. The inner liner made of polyhydroxycarboxylic acid film,preferably PSA film, is particularly suitable for flip packs. Thesecartons conventionally consist of thin card. A piece of the cartonserves to pick up the contents of the packaging, namely a collection ofcigarettes which is surrounded on all sides by the folded inner wrappingmade of polyhydroxycarboxylic acid or PSA. There is a lid disposed on aback side of the carton, which is connected to the carton over a foldline. Further details of the embodiment of flip packs are known anddescribed e.g. in DE 43 33 462, a description to which explicitreference is made here.

The collection of cigarettes, the contents of the packaging, issurrounded on all sides by the inner wrapping according to theinvention. The unit so arising as the packaging contents is a block ofcigarettes. According to the invention, a film made ofpolyhydroxycarboxylic acid, preferably a PLA film, is introduced to thecigarette wrapping in order to manufacture such a block of cigarettes.

The film is cut to the suitable width for this purpose and pulled ontothe packaging machine off a roll as a ream and cut to the appropriatelength. The shape of the cut depends on the type of folding coming intouse. For example, the tailored film cut is laid around the collection ofcigarettes according to the principle of side folding. Connected to acontinuous, closed bottom side are a front side and a back side. Anupper end wall is likewise formed by folding, such that interior pointedcorners and trapezoid pointed edges are formed.

In a further embodiment, the inner wrapping of the upper area can beprovided with a draw-off strap, a so-called flap. For this purpose aperforated line or some other kind of weakening line is made over thefull width of the cut. Upon first opening of the package, the draw-offstrap is detached by catching the outer pointed edge.

The cut is generally separated from the strips of material in such a waythat the cut lies in the longitudinal direction. The strips of materialcan be provided with printing surfaces if necessary, whichadvantageously are arranged with a gap between them in the directionrunning along the length of material. The cross cuts for dividing thecuts are carried across the film lengthwise. The exact positioning ofthe dividing line can be carried out with a print mark control becauseof the printer's imprints.

Alternatively, the cut can be constructed in such a way that the widthof the strip of film corresponds to the length of the cut. With thisarrangement, the cuts are aligned normal to the length of the strip ofmaterial. In these cases, the strip of material is provided withcontinuing strips of print on both sides, in particular of varyingwidths.

Cuts and techniques for folding the inner liner, units for imprintingcuts and further details and known in the prior art and described e.g.in DE 201 20 977 or DE 43 33 462 or DE 25 11 241, to which explicitreference is made here.

The packaging with inner liner constructed in the way described aregenerally additionally provided with an outer wrapping made of film, inparticular polypropylene film or cellophane.

According to the invention, the inner liner is made of abiaxially-oriented film, which can feature one or several layers. Themain constituent of the film is a polymer made of at least one aliphatichydroxyl carboxylic acid. In general, the film contains at least 70-100%polymers made of aliphatic polyhydroxycarboxylic acid, preferably PSA.Embodiments made of 80-99% by weight, preferably 85-95% by weight of thenamed polymers, in each case relative to the weight of the film, arepreferred.

Surprisingly, a film made of polyhydroxycarboxylic acid, preferably PLAis excellent for use as inner liner. It was found that the film fixes inplace the cigarette bundle sufficiently after the impaction. The filmshows now disruptions during handling on the packaging machine. I turnedout that the cuts have surprisingly little furling, sometimes none atall, and so avoid the problems of other thermoplastic films. Moreover,films are particularly advantageous, because with them a good stableworkability is given even in fluctuating climatic conditions. It wasshown, the in comparison the paper, fluctuating temperatures or afluctuating humidity hardly affects the film and its properties and hasno effects on its use as inner liner and can always be handled equallywell.

Both single-layered and multilayered films made of aliphaticpolyhydroxycarboxylic acid are suitable for use according to theinvention. Multilayered films are generally constructed out of a thickbase layer which features the largest layer thickness and makes up 60 to<100% of the total thickness of the film. This base layer is providedwith (a) top layer(s), preferably on both sides but only on one side ifnecessary. In further embodiments, additional intermediate layers orcoatings of the outer surface of the multilayered film are possible,through which four or five-layered, coated or uncoated, films areobtained. The thickness of the top layer generally lies in a range from0.5 to 10 μm, preferably 0.5-6 μm, in particular 1 to 3μ. The totalthickness of the film according to the invention lies in range from 20to 100 μm, preferably 25 to 80 μm, in particular 30 to 60 μm. The toplayers are the layers with form the outer layers of the film.Intermediate layers are by naturally attached between the base layer andthe top layers. Following embodiments to the layers of the film countanalogously in the same way for single-layered embodiments of the film.

Surprisingly, films with a minimum thickness of 20 μm are particularlyadvantageous for use as inner liner according to the invention. If thethickness of the film lies under 20 μm, then congestions occur on themachine. It was found that surprisingly thin films function even betterin the use according to the invention. When the film thickness is toolarge, the film shows too large reset forces, so that the wrappedcigarettes slip out of the bundle before the outer flip pack can beapplied. Therefore a maximum thickness of 100 μm should not be exceeded.

The film, as well as the individual layers of the film if necessary,contain(s) 70 to around 100% by weight preferably 80 to 98% by weight ofa polymer made of at least one of the aliphatic hydroxycarboxylic acids,hereinafter also called PHC or polyhydroxy carboxylic acids. This meanshomopolymers or mix polymerisates, which are made up of polymeristaeunits of aliphatic hydroxyl carboxylic acids. Among the PHC suitable forthe present invention, poly lactic acids are particularly suitable.These are hereinafter called PLA (poly lactic acid). Here too, bothhomopolymers which are made up only of lactic acid units, and also mixpolymerisates which predominantly contain lactic acid units (>50%)bonded with other aliphatic hydroxyl lactic acid units, are meant by theterm PSA.

As monomers of the aliphatic polyhydroxycarboxylic acids (PHC),aliphatic mono-, di- or trihydroxycarboxylic acids, or their dimercyclic esters, are suitable, among which lactic acid in its D- or L-formis preferred. These kinds of polymers are known in the prior art and arecommercially available. The manufacture of poly lactic acids is likewisedescribed in the prior art and takes place over catalytic ring-openingpolymerisation of lactide (1,4-dioxane-3,6-dimethyl 2,5-dione), thedimerised cyclic ester of the lactic acid, hence PSA is often alsocalled polylactide. The manufacture of PSA is described in the followingpublications: U.S. Pat. No. 5,208,297, U.S. Pat. No. 5,247,058 or U.S.Pat. No. 5,357,035.

Polylactic acids made up exclusively of lactic acid units are preferred.In this connexion PSA homopolymers containing 80-100% by weight L-lacticacid units, corresponding to 0 to 20% by weight D-lactic acid units, areparticularly preferred. Even higher concentrations of D-lactic acidunits can be contained as comonomers in order to decrease thecrystallinity. If necessary, the polylactic acid can additionallyfeature various aliphatic polyhydroxycarboxylic acid units as comonomersfrom the lactic acid, for example glycolic acid units, 3-hydroxypropanoic acid units, 2,2-dimethyl-3-hydroxypropanoic acid units orhigher homologues of the hydroxycarboxylic acids with up to 5 carbonatoms.

Preferred are lactic acid polymers (PLA) with a melting point of 110 to170° C., preferably from 125 to 165° C., and a melt flow index (DINmeasurement 53 735 at 2.16 N load and 190° C.) of 1 to 50 g/10 min,preferably from 1 to 30 g/10 min. The molecular weight of the PLA liesin a range of at least 10 000 to 500 000 (counting mean), preferably 50000 to 300 000 (counting mean). The glass transition temperature lies inthe Tg lies in a range from 40 to 100° C., preferably 40 to 80° C.

The individual layers of the film each contain 70 to around 100% byweight of the previously described polymers, preferably 80 to 98% byweight, as well as additional additives if necessary, like neutralisingagents, stabilisers, lubricants, static inhibitors and fillers. They areadvantageously added to the polymer or the polymer mixture beforemelting on. Phosphorous bonds, like phosphoric acids or phosphoric acidesters, for example, are introduced as stabilisers. The individuallayers can basically feature the same composition as regards polymersand additives. In general, the composition of the base layer isdifferent from the composition of the remaining layers. In particular,additives like anti-blocking agents or lubricants are added to the toplayers, whereas fillers or pigments are preferably introduced into thebase layer. Construction and composition of the individual layers of thefilm can nevertheless vary within wide boundaries.

It was found that transparent and white embodiments without vacuoles areespecially well suited for this use. It is known about polypropylenefilms that opaque PP films with vacuoles in the base layer featurebetter folding properties than transparent PP films. The vacuole-freePLA films surprisingly also show very good folding properties in thisuse in comparison to vacuolated embodiments. In the sense of the presentinvention, transparent films are to be understood as those with a lightpermeability according to ASTM-D 1003-77 lies over 75%, preferably over95%. White PLA films are coloured white by the addition of whitepigment, but have no vacuoles either. These embodiments generallycontain TiO₂ in a quantity of 1-12% by weight in at least one layer, ifnecessary several. Basically, TiO₂ can be added in these quantities toone or both top layers or also to one or both intermediate layers.

The addition of opaque or white-opaque embodiments of the film isbasically also possible. These films contain vacuole-initiating fillersin the base layer, for example cycloolefin copolymer (opaque films) and,if necessary, additional pigments (white-opaque films). In this case,too, TiO₂ is also preferred as pigment and is introduced in a quantityof up to 10% by weight, preferably 1 to 8% by weight, in each caserelative to the base layer.

If necessary, the film can be coated in order to optimise furtherproperties of the film. Typical coatings are adhesion-enhancing,slip-improving or dehesive-operating coatings. If necessary, theseadditional coatings can be applied over in-line coating by means ofaqueous or non-aqueous dispersions before lateral stretching oroff-line.

In a further embodiment, the films are metallised as inner liner beforeuse. Upon use as inner-liner, the metallised side forms the visibleside. In a further embodiment, the film can be metallised on both sides.This embodiment has the additional advantage that direct contact betweenthe cigarettes and the film is avoided, so that no detriments to thetaste of the cigarettes because of the film are possible, or rather theyare extensively prevented.

In a further embodiment, the metallised or non-metallised film can beadditionally provided with an embossment which on the one hand has adecorative character, and which contributes towards a further improvedflatness. Surprisingly, after metallisation and imprinting the films canbe handled just as well as the paper inner-liner used until now. What ismore, the embossed metallised films come very close to the topicalappearance of metallised papers.

The PHC film is manufactured according to the coextrusion procedureknown in itself. Within the scope of this procedure, the melt(s)corresponding to the layers of the film are coextruded through a flatdie, the multilayered film so obtained is pulled off for hardening onone or several roller(s), the film is subsequently biaxially stretched(oriented), the biaxially-stretched film is heat set and, if necessary,corona- or flame-treated on the surface layer intended for treatment.

The biaxial stretching is generally carried out sequentially. In sodoing, stretching preferably happens first in the longitudinal direction(i.e. in the machine direction, =MD direction) and subsequently in thelateral direction (i.e. at a right angle to the machine direction, =TDdirection). This leads to an orientation of the molecular chains. Thestretching in the longitudinal direction preferably takes place with thehelp of two rollers running at different speeds, corresponding to thedesired stretch ratio. For the lateral stretching, a corresponding clipframe is commonly used. Further description of the film manufacture iscarried out according to the example of a flat film extrusion withsubsequent sequential stretching.

The melt(s) are pressed through a flat die (sheet die), and the filmpressed out is pulled off on one or several outfeed rollers at atemperature of 10 to 100° C., preferably 20 to 80° C., such that itcools off and hardens.

The film so obtained is then stretched along and across the direction ofextrusion. The longitudinal stretching will preferably be carried out ata roller temperature of the stretch roller of 40 to 130° C., preferably50 to 100° C., advantageously with the help of two rollers running atdifferent speeds, corresponding to the desired stretch ratio; thelateral stretching preferably at a temperature of 50 to 130° C.,preferably 60 to 120° C. with the help of a corresponding clip frame.The longitudinal stretch ratios can vary within a range of 1.5 to 8. Inthe manufacture of films with a base layer containing vacuole-initiatingfillers a high longitudinal stretch ratio of 3 to 6 is preferred,whereas films with a transparent base layer are preferably stretchedwithin a range of 1.5 to 3.5. The lateral stretch ratios lay in therange from 3 to 10, preferably 4 to 7.

Attached to the stretching of the film is its heat setting (heattreatment), where the film is held converging around 0.1 to 10 s long ata temperature of 60 to 150° C. (convergence up to 25%). Subsequently thefilm is wound up in the conventional manner with a batcher.

The following measured values were used to characterise the rawmaterials and the films:

The invention will hereinafter be explained on the basis of thefollowing execution examples:

EXAMPLE 1

A transparent, three-layered PLA film with a thickness of around 30 μmwas manufactured by extrusion and subsequent incremental orientation inthe longitudinal and lateral directions. The base layer consisted ofalmost 100% by weight polylactic acid with a melting point of around160° C. The layer additionally contained stabilisers and neutralisingagents in conventional quantities. Both sealable top layers werefundamentally made up of an amorphous polylactic acids such that thispolylactic acid features an L/D ratio of around 40/60. In addition, thetop layers each contained 0.1% y weight SiO₂-based particles asanti-blocking agents. The thickness of the top layers each came to 2.5μm.

The manufacturing conditions in the individual procedural steps were:

Extrusion: temperatures 170-200° C.

Temperature of the outfeed roller: 60° C.

Longitudinal stretching: temperature: 68° C.

Longitudinal stretch ratio: 2.0

Lateral stretching: temperature 88° C.

Lateral stretch ratio (effective): 5.5

Fixation: temperature 75° C.

Convergence: 5%

EXAMPLE 2

A film was manufactured as is described in example 1. In contrast toexample 1, no top layer was attached. For the rest, the composition andthe manufacturing conditions were unchanged. A transparent film, but asingle-layered film with a thickness of 25 μm, was again manufactured.

EXAMPLE 3

By extrusion and subsequent incremental orientation in the longitudinaland lateral directions, an opaque, single-layered PLA film with athickness of 30 μm was manufactured. This layer was around 95% by weightmade up of a polylactic acid with a melting point of 135° C. and a meltflow index of around 3 g/10 min and a glass transition temperature of60° C. and around 5% by weight COC (Ticona Topas 6013) with a Tg of 140°C. The layer additionally contains stabilisers and neutralising agent inconventional quantities. The manufacturing conditions in the individualprocedural steps were:

Extrusion: temperature 170-200° C.

Temperature of the outfeed roller: 60° C.

Longitudinal stretching: temperature: 68° C.

Longitudinal stretch ratio: 4.0

Lateral stretching: temperature: 88° C.

Lateral stretch ratio (effective): 5.5

Setting: temperature: 75° C.

Convergence: 5%

In this way, an opaque film with characteristic pearlescent shine and areduced density of around 0.75 g/cm³ is obtained.

The films were introduced on a commercial cigarette packaging machine asinner liner and could be used without huge problems. The non-vacuolatedfilms according to example 1 and 2 showed themselves to be especiallyadvantageous. In contrast, biaxially oriented polypropylene films couldnot be adopted in this usage. Because of strong reset forces of thematerial, the individual cigarettes could not be packaged.

Unrecognised Text

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1-16. (canceled)
 17. An inner liner for a cigarette packaging whichcomprises a single-layered or multilayered, biaxially-oriented filmwhich contains 70 to 100% by weight of polymer of at least one aliphaticpolyhydroxycarboxylic acid.
 18. The inner liner according to claim 17,wherein the film is transparent.
 19. The inner liner according to claim17, wherein the film is white.
 20. The inner liner according to claim17, wherein the film has an opaque, vacuolated base layer.
 21. The innerliner according to claim 17, wherein the film is metallized on onesurface.
 22. The inner liner according to claim 17, wherein the film ismetallized on both sides.
 23. The inner liner according to claim 17,wherein the film is embossed.
 24. The inner liner according to claim 21,wherein the metallized surface of the film is embossed.
 25. The innerliner according to claim 17, wherein the film contains 80 to <98% byweight of a polymer of aliphatic polyhydroxycarboxylic acid in the baselayer.
 26. The inner liner according to claim 17, wherein film featurestop layers on both sides, and the top layers contain 70 to <100% byweight of a polymer of aliphatic polycarboxylic acid.
 27. The innerliner according to claim 17, wherein the aliphatic polyhydroxycarboxylicacid is a polylactic acid.
 28. The inner liner according to claim 17,wherein the film has a total thickness of 20 to 100 μm.
 29. The innerliner according to claim 17, wherein the top layer has thickness of 0.5to 6 μm.
 30. The inner liner according to claim 17, wherein the toplayer is sealable.
 31. A cigarette packaging which comprises the innerliner according to claim 17
 32. The cigarette packaging as claimed inclaim 31, wherein that cigarette packaging is a flip pack.
 33. Thecigarette packaging as claimed in claim 31, wherein that cigarettepackaging is a soft packaging.